A new genus and species of azooxanthellate solitary coral, Monohedotrochus capitolii, are described in the subfamily Caryophylliinae, based on 42 specimens, most collected off Santa Catarina and Rio Grande do Sul states, southern Brazil. The new genus is characterized by being solitary and attached, having a monocyclic base, hexamerally arranged septa in four or five cycles, lacking paliform lobes and having a papillose columella. Oxysmilia epithecata Cairns, 1999, and O. circularis Cairns, 1998, are transferred to the new genus.